Consonants that won't be silent

In almost all nouns, the letters 's' and 't' are silent if they are the last letters in the word, e.g. le fait, le pas, le secret. There are, however, a few words where these consonants are pronounced and these simply need to be learnt. These words include:

le but               goal
le bus              bus
le médium        medium (word ends in -ium)
la dot               dowry
l'os                  bone (the 's' is pronounced only in the singular)
le pénis            penis
l'anus               anus (I really have no idea what the deal is with some body parts. Perhaps
                       the endings -us and -is are taken from Latin)
l'oued              wadi